Most strobe driver units are designed with
filtering and internal shielding to keep radio interference to a minimum, however
occasionally noise will be heard over the radio or intercom This noise is almost always
caused by the way the systems have been installed.
One must remember that noise does not always come
from the power that is being supplied to your equipment. Especially if the radio has it's
own power source (battery ) and the strobe is powered by the aircraft battery.
Installations vary greatly from aircraft to aircraft. Do both systems share the same power
source? Is there an external antenna? How close is the antenna, radio, wires, etc. to the
strobe driver box and wiring? If both systems are not sharing the same power, then where
is the common thread? In most, if not all cases the problem is GROUNDING.
The ground path
is very, very important. The strobe circuit draws high current through the ground circuit.
The radio, intercom, head set and mike circuits use that same ground so it is important
that there is NO voltage drop between where all these grounds are connected. In other
words lets say the strobe driver is getting negative battery or ground from a bus near the
battery that is also grounded to the metal frame of the aircraft.
The ground plane for the
radio antenna is connected to the aircraft frame further back near the tail and the radios
are grounded near the cockpit to a screw in the frame. This array of connections can be a
source of noise. The following list is intended to help in eliminating noise.
1. Power for the strobe system should be on the first fuse of the
power bus. In other words the closest fuse to the battery.
2. The strobe driver's metal case should be solidly connected with
a ground strap or 16 ga. wire to the aircraft ground system.
3. The audio ground and aircraft ground
should be commonly connected only at ONE SINGLE POINT. Ground all the audio equipment;
radio, mike, antenna, headphones, intercom, etc. to an "audio ground bus" (16
ga. or larger wire). Then connect that bus at one end only to the aircraft central
grounding point, preferably near the point the battery is grounded.
4. Do not run audio related wires next to power supply wires.
5. Shielded wire is not normally necessary, however, if it is
being used ground that shield at only ONE end. Usually the end closest to the source.
This list has been derived from the fixes that have worked for
others. if you find something new please let us know and yours will be added to help
someone else.
